In ordinary daily life, all kinds of lighting apparatus can be seen everywhere, such as fluorescent lamps, street lamps, table lamps, artistic lamps and so on. In the above-described lighting apparatus, the tungsten bulb is traditionally used as a light-emitting light source. In recent years, due to the ever-changing technology, light-emitting diode (LED) has been used as a light source. Moreover, in addition to lighting apparatus, for the general traffic signs, billboards, headlights etc., light-emitting diode has also been used as a light source. The light-emitting diode as a light source has the advantages of energy-saving and greater brightness. Therefore, it has been gradually common.
With the popularity of LED lamps, LED lamps are used in more and more occasions, but as we all know, LED lamps are powered by a dedicated LED power supply. At the same time, with the improvement of living standard, people need to the LED lamp with variable brightness. Therefore, the LED power with variable output is needed. In the prior art, there are many LED power supplies with variable output that can change the output brightness of the LED lamps. However, these LED power supplies in some cases do not give users a very good experience of using light, for example in display lighting or in the museum, many users prefer to use a mobile phone or a camera to photograph the displayed items. However, the existing LED power supply with variable output power makes the light source provided by the LED lamp form a lot of photos taken by the mobile phone or the camera and make the picture distorted, affect the user's light experience.
In the prior art, the brightness of the LED lamp is adjusted by using a current adjusting method, which can avoid the phase flash. But this method is generally applicable to a constant current lamp or lamp group. For unknown constant current value flowing through a lamp or lamp group, such as in a freezer or showcase, the customer does not know how many lamps form a lamp group, but only want to use a constant-voltage dimming power supply. Because the current flowing through the lamp system is unknown, it is difficult to obtain an effective dimming effect by using the existing current dimming method. For example, when the total current of the lamp group is greater than the maximum dimming current in the existing dimming method, and the maximum dimming current is exceeded, the existing current dimming method is often ineffective, and a phenomenon of dead zone will appear.